Animal studies of retinal degeneration demonstrate that primary rod cell death is associated with secondary cone cell degeneration of relatively slow time course. This degeneration involves the loss of the outer segments of the cones and a dislocation of elements of the cone inner segments to the perikaryon while the typical inner segment disappears. From extensive studies on the rd (RCS) rat, these remnant cone-cells lacking cones ("coneless") are photoreceptive and feed visual information on to the neuronal network of the inner layers of the retina. Visual capabilities of the animal are preserved to a remarkable degree. These capabilities diminish and finally disappear with the aging of the animal and the reduction in number of the remnant cone cells. The pathohistology of human retinitis pigmentosa shows survival of much the same remnant cone cells outside the parafovea and their disappearance with age. Cone cell mediated functions outside the central region have not been studied in the past to any great degree. The proposed study attempts to classify and analyze surviving cone cell functions in the non-central parts of the visual field of retinitis pigmentosa patients by measuring extensively several sets of psychophysical functions in two pairs of selected patients with different visual field constriction and different inheritance type at different retinal loci of subnormal sensitivity using forced choice paradigms.